Prior patents featuring vibratory sound amplification have generall related to stethoscopes in which a transducer is utilized for monitoring heart beats or the sound of blood produced in passing through heart valves, even detecting of fetal heart beats.
Although electronic devices for sensing insect-induced vibrations have been constructed in the past, such devices had only limited practicability due to the need for conflicting design parameters. Such devices need to be extremely sensitive to pick up the subtle vibrations in a structure or other article caused by insects. Yet if such sensitivity was achieved, the device also picked up a large variety of vibrations caused by other phenomena, as well as human activity. This has typically limited the usefulness of such prior art devices to laboratory-type environments.
R. C. Barton in "An Audio-Amplifying System for Termite Detection," Termites and Termite Control, 1934, pp. 711-714, discloses an early attempt to develop an audio-amplifying system for termite detection. The system used a phonograph-type needle as a probe which was actually inserted into the article under inspection, such as a wall, for detecting the mechanical vibrations in the object being inspected. The author apparently tried other transducers, such as an electrical stethoscope, but without the level of success that he had with the phonograph needle. The electrical signals from the needle transducer were then amplified and filtered prior to being transmitted to earphones. The article clearly indicates at p. 714, however, that the system was not successful out of a laboratory environment and, in addition, was too costly to be practical.
Another article also discloses a device for invasively detecting termites in a laboratory environment, Roy J. Pence, "Electronic Detective Developed by UCLA Uncovers Termites," Pest Control, Nov., 1954, p. 27. The device described in this article comprises a transducer having a needle probe which is actually inserted in the material to be inspected, and an amplifier which amplifies the portion of the electrical signals generated by the needle-type transducer which falls within a preselected frequency range. The article expressly indicates that its value is as a laboratory tool.
There is additionally a marketing brochure "Electronic Termite Detection", Physionics Corportion, (publication date unknown), that discloses an electronic termite detector which comprises a hand-held probe-type transducer, an amplifier for amplifying electrical signals generated by the probe which are within a specified frequency range, and earphones. Although the initial Instructions in the brochure indicate that it is only necessary to hold the probe firmly against the surface being inspected, a subsequent supplement to the instructions states that the operator should use a Safety Needle which was included with the device, both to protect the probe and crystal element and to allow greater clarity in listening to termites, by eliminating any noise generated by operator contact with the probe. None of the devices described in the publications are suitable for detecting insects in particulate matter, such as wheat, rice, or the like.
The invention is distinctive over the prior art by providing a piezoelectric transducer mechanically and directly connected to a probe or noise detection structure capable of detecting vibrations or noise in particulate matter infested with insects or larvae. The inventive device minimizes the conversions of energy because of the direct physical contact between the vibration receiving structure and the piezoelectric crystal. The apparatus will detect sounds generated by the movement, eating or other destruction of flour beetles, rice weevils, Indian grain moths, and other grain destroying insects in grain bins, trucks or other storage areas, and amplify those sounds sufficiently to permit an operator to hear such vibrations through a headset. The frequency ranges of those movements vary from 350 to 3,500 Hertz, and in a narrower range from 750 Hertz to 1500 Hertz depending upon the grain (milo, corn, wheat, rice, flax, etc.) and the insect making the noise. The movement pattern made by different insects due to varying sizes and speed of movement makes it possible to analyze the patterns and identify which insect is making the noises picked up through the transducer.